Stockfish chess

Do you mean their iOS app? Does it give an elo level estimate? On the Windows app it's just a skill level from 0 to 20, and you can't really say it's inaccurate, since it's not being compared to an elo scale.

If you mean the level for the engine to play at, as a handicap, it's an approximation. Most engines limit their calculation time and depth as you reduce from the maximum, then may even add in arbitrary bad moves as it goes lower. But no, it isn't anywhere near exact.

I like Hiarcs 14 for setting the engine's strength. It's the most human like feel I've found in an engine, when handicapped or at full strength. It seems to play stronger than the actual weakened Elo set at though. Against me Chessmaster 10's preset players usually played some type of off the wall move in order to lower it's full strength, such as giving up a knight for a pawn on move 12 for no reason whatsoever.

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